Hi all !
I just want to share a conversation I had a while ago about processed film conservation with a very helpful engineer at the Image Permanence Institute (@ RIT). I was interested by a few points that may interest you also. Here are the conclusions I got:
1- a small quantity of Hypo in BW materials actually helps protecting the image from polution. This cannot be traduced to operational steps as the danger of under-washing is existing and no one can say exactly how to get very small, controlled remaining quantities of Hypo. One thing is sure: Over washing is useless.
2- The best thing to protect films (color or BW) is closing them in a freezing bag with dessicant and freeze them.This effectively copes with dyes migration in color materials. Keeping them in a refrigerator is good on a temperature point of vue but is really a problem about humidity. Don't try it...
3- Humidity tends to allow the emulsion to be more porosive and thus more receptive to pollutant. Keeping films in low humidity is the best way after freezing to protect inherently stable materials (read B&W or Kodachrome).
As I decided that all the fuss around freezing is a bit too much and I aint gonna buy a new freezer, for me, #3 was a great advice. I have bought raw Silicagel, stuffed it in socks and closed my neg filers in freezing bags with them and back to my closet. My camera bags are also full of socks now
BTW, even if you put aside chemical pollution, humidity can help mold to develop on your negs and I heard this one is a real killer!
If someone is interested by more details and theory, please send me a mail and I'll forward the original mail "conversation".